Field of the Invention
The present invention relates to a ceramic heater capable of heating, for example, a semiconductor wafer and to an electrostatic chuck used, for example, in fixing a semiconductor wafer, in correcting flatness of a semiconductor wafer, and in transporting a semiconductor wafer.
Description of Related Art
Conventionally, a semiconductor fabrication apparatus has performed, for example, dry etching (e.g., plasma etching) on a semiconductor wafer (e.g., a silicon wafer). Since, in order to enhance accuracy of dry etching, the semiconductor wafer must be securely fixed, an electrostatic chuck has been proposed as means for fixing the semiconductor wafer. The electrostatic chuck fixes the semiconductor wafer by electrostatic attraction.
Specifically, the electrostatic chuck, for example, has internal chucking electrodes in a ceramic substrate (ceramic insulation plate). By use of electrostatic attraction generated through application of voltage to the chucking electrodes, the electrostatic chuck chucks the semiconductor wafer on the upper surface (first main surface or chucking surface) of the ceramic substrate. The electrostatic chuck is configured such that a base substrate (metal base) is bonded to the lower surface (second main surface or bonding surface) of the ceramic substrate.
Furthermore, a certain known electrostatic chuck has a function of adjusting (heating or cooling) the temperature of a semiconductor wafer chucked on the chucking surface. For example, according to a known technique, a heat-generating element (e.g., linear heat-generating conductor) is disposed in the ceramic substrate, and the heat-generating element heats the ceramic substrate to thereby heat the semiconductor wafer on the chucking surface. Also, according to another known technique, a cooling path is provided in the metal base for flowing cooling fluid therethrough to thereby cool the ceramic substrate.
Such an electrostatic chuck usually has, for example, lift pin holes formed therein for accommodating respective lift pins used to assist attachment and detachment of the semiconductor wafer, and a gas hole formed therein for supplying a heat transfer gas (backside gas) to an interface between the semiconductor wafer and the chucking surface of the electrostatic chuck.
Also, according to a recently developed ceramic heater, in order to accurately heat the electrostatic check, etc., the ceramic substrate is divided into a plurality of heating zones (heater zones). Specifically, a proposed ceramic heater has multiple zone heaters such that heating zones have respective heat-generating elements (zone heat-generating elements) capable of independently heating the heating zones, thereby enhancing the function of adjusting the temperature of the ceramic substrate (refer to Patent Documents 1 and 2).